Australia: The Land Where Time Began

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Reply to comment on “Trace fossil evidence for Ediacaran bilaterian animals with complex behaviors”

Retallack argues that the Shibantan trace fossils were made by motile grex phase cellular moulds such as Dictyostelium discoideum, which is a terrestrial eukaryote, and not by bilaterian animals. He also indicates, based on this reinterpretation the Shibantan traces, that they are terrestrial, suggesting that the hosting limestone could be palaeosols. Chen et al. say that though the slime mould interpretation is interesting it can be falsified on the grounds of petrographic observations. They add that the trace makers in the Shibantan deposit were capable of excavating and displacing sediments (Chen et al., 2013), splitting microbial mats rich in clay to construct persistent tunnels (Chen et al., 2013, Fig. 2C & D), and truncating and deforming microbial laminae (Chen et al., 2013, Fig.6F). Though sub-millimetre-sized surface trails can be left by some slime moulds on agar gel, Chen et al. say they know of no slime moulds that are known to be capable of displacing and excavating intraclastic sediments, constructing millimetre-sized tunnels within sediments, and the truncation of sedimentary laminae. In this reply Chen et al. respond briefly to Retallack’s specific comments.

Sources & Further reading

  1. Chen, Z., C. Zhou, M. Meyer, K. Xiang, J. D. Schiffbauer, X. Yuan and S. Xiao (2013). "Reply to comment on “Trace fossil evidence for Ediacaran bilaterian animals with complex behaviors” [Precambrian Res. 224 (2013) 690–701]." Precambrian Research 231(0): 386-387.


Author: M. H. Monroe
Last updated: 20/04/2015
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